Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Heart failure wikipedia , lookup
Coronary artery disease wikipedia , lookup
Lutembacher's syndrome wikipedia , lookup
Myocardial infarction wikipedia , lookup
Antihypertensive drug wikipedia , lookup
Electrocardiography wikipedia , lookup
Cardiac surgery wikipedia , lookup
Quantium Medical Cardiac Output wikipedia , lookup
Heart arrhythmia wikipedia , lookup
Dextro-Transposition of the great arteries wikipedia , lookup
Review: The Cardiac Cycle 1. Label the diagram of the heart in as much detail as you can. 2. Annotate the next three diagrams to show the different stages of the cardiac cycle. What structure? 3 of 24 © Boardworks Ltd 2008 The cardiac cycle 4 of 24 © Boardworks Ltd 2008 Myogenic stimulation of the heart 5 of 24 © Boardworks Ltd 2008 Today we are covering from the specification: How is the nervous system organized? 7 of 38 © Boardworks Ltd 2009 Control of Heart Rate Autonomic Sympathetic Positive stimulation (speed up activity) Uses the neurotransmitter noradrenaline. Parasympathetic Inhibitory (slows down activity) Uses the neurotransmitter acetylcholine. Control of heart rate Heart rate is controlled by the part of the brain called cardioregulatory centre in the medulla oblongata Has two centres: 1.Acceleratory centre - Increases heart rate (linked to the sinoatrial node by the sympathetic nervous system) 2.Inhibitory centre - Decreases heart rate (linked to the sinoatrial node by the parasympathetic nervous system) The centre that is stimulated depends on: •Chemical changes in the blood •Pressure changes in the blood Control by chemoreceptors Found in the walls of the carotid artery and aorta (in the carotid and aortic bodies). Sensitive to changes in the pH of the blood that result from changes in carbon dioxide concentration (in solution CO2 forms carbonic acid.) When the blood has a higher than normal concentration of CO2, pH decreases. Chemoreceptors in the wall of the carotid arteries and the aorta detect this. Frequency of nervous impulses to the cardioregulatory centre increases. Frequency of impulses from accelerator centre via sympathetic NS to the SAN is increased. Heart rate increases. Heart rate increases. The increased blood flow that this causes leads to more CO2 being removed in the lungs so CO2 levels return to normal. Chemoreceptors are no longer stimulated, so send fewer impulses to the cardioregulatory centre. Fewer impulses are sent from the accelerator centre to the SAN so heart rate decreases back to normal. Control by pressure receptors Pressure receptors (baroreceptors) occur within the walls of the carotid arteries and the aorta. http://www.youtube.com/watch?v=G2nLL_O_U7w When a blood pressure is higher than normal: 1) Nervous impulses are transmitted to the cardioinhibitory centre. 2) Impulses are sent via the parasympathetic nervous system to the SAN, decreasing heart rate. Control by pressure receptors When a blood pressure is lower than normal: 1) Nervous impulses are transmitted to the cardioacceleratory centre. 2) Impulses are sent via the sympathetic nervous system to the SAN, increasing heart rate. N.B. This system relies on the different neurotransmitters released at the SAN by the two systems. Brain Cardioaccelerator centre Cardioinhibitory centre Medulla oblongata Spinal cord Carotid body Sympathetic nerve Carotid arteries Aortic body Parasympathetic nerve SAN AVN Right atrium Right ventricle Aorta Left atrium Bundle of His Left ventricle Try the questions on p142-143.